Sacrificial layer-assisted one-step transfer printing for fabricating a three-layer dry electrode

A sacrificial-layer assisted one-step transfer printing method is presented to fabricate a three-layer dry electrode for detecting electrophysiological signals. First, an Au electrode layer was deposited on a silicon wafer covered by a Cu sacrificial layer. Then, a polyimide (PI) intermediate layer was patterned on the Au layer by a standard photolithography process, and subsequently the Au layer was patterned by wet etching, using the patterned PI layer as the etching mask. Finally, both the patterned Au layer and PI layer were transferred onto a stretchable film in one step to make a three-layer dry electrode by etching away the Cu sacrificial layer. This three-layer dry electrode exhibited excellent conformability and stretchability and low electrode-skin contact impedance. The performance of the three-layer dry electrode for long-term and dynamic electrocardiogram (ECG) monitoring was also examined. The quality of ECG signals was well maintained for 48 h, during which period the signal to noise ratio was kept at 40 dB. It was also found that the physical exercises had only slight effects on the ECG signal, where all features of the signal were clearly distinguishable when the volunteer ran at 5 km/h. (C) 2020 Elsevier B.V. All rights reserved.